Commutators are routinely used to control the flow of electrical energy in rotating electrodynamic machines such as motors and generators. One typical commutator construction consists of a cylindrical ring of commutator bars supported by and positioned around an insulating hub. Tangs for electrical connections normally extend from one end of each commutator bar, and the bars are normally provided with inwardly extending anchoring bars to secure the bars to the insulating hub. The bars are normally slit from a cylindrical shell, produced by shaping a formed strip of metal into a cylindrical shell, molding the insulating hub inside the shell and slitting the shell to form the individual commutator bars.
The formed strips from which the cylindrical shells are produced are conventionally made from a single strip of copper or other metal by single stage or progressive forming techniques which are known by designations such as coin-lug design, casselated design, skived design, grooved design and the like. In all of these techniques the tangs and anchoring tabs are formed on a single strip of metal by single stage or progressive tooling. All of these techniques suffer from certain common problems. They require expensive tooling, do not provide optimal dimensional control and do not allow desired balance between bar weight and locking lug positions. This leads to excessive rejection rates, parts with excessive variations in dimensions or unbalanced centripetal forces, which in turn can lead to reduced performance and higher failure rates.